[0001] This invention relates to electro-optic devices and in particular to optically addressed
electro-optic devices.
[0002] EP-A-488455 describes an electro-optic device which comprises a substrate carrying
an addressable matrix device such as a liquid crystal display device or an image sensor.
The rows and columns of the matrix array of display pixels or imaging elements are
accessed by supplying signals along row and column conductors using an electro-optic
switching arrangement which comprises photosensitive elements provided on the substrate
carrying the matrix array. In the arrangement described in EP-A-488455, the photosensitive
elements are driven by a linear array of light emitting devices such as light emitting
diodes or the like. Each row (or column) conductor is associated with a unique pattern
of photosensitive elements with each photosensitive element being located at the intersection
of the row (or column) with a column (or row) conductor so that by activating a given
set of the linear light emitting devices a given set of column (or row) conductors
and the associated photosensitive elements are illuminated causing the photosensitive
elements to conduct. Each unique, pattern of illumination of the linear light emitting
devices corresponds to a unique arrangement of photosensitive elements and accordingly
when a selected given set of light emitting devices is activated all of the photosensitive
elements associated with a unique row (or column) conductor will conduct so coupling
that row (or column) conductor to the associated drive circuitry. Such an arrangement
enables a reduction in the number of components and allows there to be comparatively
few external connections to the electro-optic device.
[0003] According to the present invention, there is provided an electro-optic device comprising
a first substrate carrying an electro-optic display having a first array of display
elements and conductors for addressing individual display elements to enable the display
to display an image, a second substrate carrying a second array of elements addressable
by conductors and photosensitive elements associated with the conductors for supplying,
when illuminated, signals along the conductors for accessing the elements of the second
array, the second substrate being provided opposite the first substrate so that the
photosensitive elements are associated with selected ones of the display elements
for enabling the selected display elements to illuminate the photosensitive elements
allowing access of the elements of the second array to be controlled by the display.
[0004] Thus, in an electro-optic device in accordance with the invention an electro-optic
display for displaying images to a user of the device is used to enable elements carried
by a second substrate to be optically addressed so that it is not necessary to provide
separate drive circuitry for the element array carried by the second substrate so
allowing for a reduction in the drive circuitry required and thus simplifying and
reducing the costs of the manufacture of the electro-optic device, especially of the
second array.
[0005] As used herein the term electro-optic display means any device capable of producing
a spatial pattern of light which is controlled electrically, for example a liquid
crystal display (LCD) or other similar display or a cathode ray tube (CRT) especially
a flat CRT.
[0006] The electro-optic display may comprise a two-dimensional matrix array of display
elements arranged in row and columns with associated row and column conductors and
the second array may be a two-dimensional array of elements arranged in rows and columns
with row and column conductors being associated with the elements of the second array
so that supplying signals to a selected row conductor and a selected column conductor
of the second array accesses an element of the second array and the row and column
conductors of the second array being associated with photosensitive elements for supplying,
when illuminated by selected ones of the display elements, signals along the row and
column conductors for accessing the elements of the second array. However, the present
invention could be applied to a situation in which at least one of and possibly both
the display and the second array is a one dimensional array.
[0007] Generally, the photosensitive elements are arranged at the periphery of the second
array so facilitating their protection against undesired illumination from sources
other than the display and reducing any disturbances of the normal functioning of
the second array which might otherwise arise.
[0008] Each conductor of the second array may be associated with a respective photosensitive
element.
[0009] In an alternative arrangement, each conductor of the second array may be associated
with a number of photosensitive elements arranged such that signals are only supplied
along the conductor when all of the associated photosensitive elements are illuminated.
For example an appropriately modified version of the arrangement described is EP-A-488455
could be used.
[0010] The photosensitive elements associated with adjacent conductors may be staggered
so that the spacing between the photosensitive elements associated with adjacent conductors
is greater than the spacing between adjacent conductors. This should reduce any possibility
of optical cross-talk between adjacent photosensitive elements, that is it should
reduce the possibility of accidental illumination of photosensitive elements adjacent
the photosensitive element intended to be illuminated.
[0011] In one example each element of the second array is arranged to store charge and each
row conductor of the second array is coupled to a select voltage supply line via at
least one respective photosensitive element so that in operation of the electro-optic
device in order to read charge stored at the element within a row the at least one
photosensitive element associated with the row is illuminated by the display to couple
the select voltage to the row conductor. Each row conductor of the second array may
be coupled to a reset voltage supply line via at least one respective switching element
for enabling a reset voltage pulse to be applied to the row conductor to reset the
associated elements.
[0012] Each column conductor of the second array may be connected by at least one first
photosensitive element to one electrode of a respective column capacitor having its
other electrode coupled to a charge sensitive amplifier and to at least one second
photosensitive element which is coupled to a voltage reference line so that, in order
to read charge from an element within a given column of the second array, first the
associated at least one first photosensitive element is illuminated by the display
for allowing the charge stored at an element in both the column and a row to which
the select voltage is applied to be transferred via the column conductor and the at
least one first photosensitive element to the capacitor and then the at least one
second photosensitive element is illuminated to allow the charge stored at the column
capacitor to be transferred to the charge sensitive amplifier.
[0013] In another example, each column conductor may be coupled to one electrode of each
of first and second column capacitors by respective first photosensitive elements
with each capacitor having its other electrode coupled to a respective charge sensitive
amplifier and to a respective second photosensitive element coupled to a voltage reference
line so that, in order to read charge from an element within a given column of the
second array, first one of the associated first photosensitive elements is illuminated
by the display for allowing the charge stored at an element in both the column and
a row to which the select voltage is applied to be transferred via the column conductor
and the said one first photosensitive element to the associated one of the first and
second capacitors and then the one of the second photosensitive elements is illuminated
to allow the charge stored at the column capacitor to be transferred to the charge
sensitive amplifier.
[0014] The spacing between the photosensitive elements associated with adjacent conductors
may be greater than the spacing between the adjacent conductors so as to reduce the
possibility of cross-talk. The first and second arrays may be of comparable size and
the display elements for illuminating the photosensitive elements may be provided
at the periphery of the first array so avoiding or at least reducing any disturbance
in the normal function of the first array. The display may comprise a liquid crystal
display.
[0015] The second array may comprise an array of further photosensitive elements so that
the second array forms an image sensor provided on top of the display enabling, for
example, the optical input of data into the display. As possible alternatives, the
second array could comprise a further display which can be used to modulate the display
output of the display carried by the first substrate. Additionally the second array
could be any suitable form of electro-optically programmable memory, for example,
a thin film memory. The second substrate carrying the second array may be mounted
to the first substrate carrying the first array. The second substrate carrying the
second array may be separable from the first substrate carrying the first array.
[0016] Embodiments of the invention will now be described, by way of example, with reference
to the accompanying drawings, in which:
Figure 1 shows a simplified schematic perspective view of an electro-optic device
in accordance with the invention;
Figure 2 shows one example of a circuit layout for the display of an electro-optic
device in accordance with the invention;
Figure 3 shows one example of a circuit layout for the second array of an electro-optic
device in accordance with the invention;
Figure 4 is a schematic fragmentary plan layout showing an example of one possible
layout for the second array of an electro-optic device in accordance with the invention;
Figure 5 is a cross-sectional view taken along the line V-V in Figure 4;
Figure 6 is a cross-sectional view taken along the line VI-VI in Figure 4;
Figure 7 is a cross-sectional view taken along the line VII-VII in Figure 4;
Figure 8 is a cross-sectional view taken along the line VIII-VIII in Figure 4;
Figure 9 is a cross-sectional view similar to Figure 8 of a modified version of the
second array shown in Figure 4;
Figure 10 shows graphically the changes in voltages applied to a row conductor with
time t for explaining operation of a device in accordance with the invention;
Figure 11 shows a modified version of the circuit layout shown in Figure 3;
Figure 12 is a schematic plan view of part of the circuit layout of the second array
of an electro-optic device in accordance with the invention for illustrating one example
of an arrangement for the photosensitive elements; and
Figure 13 is a schematic plan view of part of the circuit layout of the second array
of an electro-optic device in accordance with the invention for illustrating another
example of an arrangement for the photosensitive elements.
[0017] It should of course be understood that the drawings are merely schematic and are
not to scale. Like parts are referred to throughout the drawings by like reference
numerals.
[0018] Referring now to the drawings an electro-optic device 1 is shown which comprises,
as illustrated very schematically in Figure 1, a first substrate 2 carrying an electro-optic
display 3 having a first array 4 of display elements 5 and conductors 12,13 for addressing
individual display elements 5 to enable the display to display an image, a second
substrate 6 carrying a second array 7 of element 8 addressable by conductors 9,10
and photosensitive elements 11 associated with the conductors 9,10 for supplying,
when illuminated, signals along the conductors 9,10 for accessing the elements 8 of
the second array 7, the second substrate 6 being provided opposite (as shown over
or on top of) the first substrate 2 so that the photosensitive elements 11 are associated
with selected ones 5' of the display elements 5 for enabling the selected display
elements 5a to illuminate the photosensitive elements 11 allowing access of the elements
8 of the second array 7 to be controlled by the display 3.
[0019] The fact that the second array 7 can thus be accessed or driven by the display 3
means that it is not necessary to provide separate drive circuitry for the second
array.
[0020] In the examples illustrated in the drawings and as shown most clearly in Figures
2 and 3, respectively, the electro-optic display 3 comprises a two-dimensional matrix
array 4 of display elements 5 arranged in rows n
d and columns m
d. The second array 7 is similarly a two-dimensional array of elements 8 arranged in
rows and columns n
e and m
e. In the interests of clarity the elements 5 and 8 are illustrated merely as blocks
in Figure 1.
[0021] The electro-optic display 3 may be of any suitable conventional type but is in this
example a liquid crystal display formed on a suitable transparent substrate, for example
a glass or plastics substrate 2. The display elements 5 are connected in rows n
d and columns m
d by row and column conductors 12 and 13 to which signals are supplied for accessing
or driving individual display elements or pixels 5 by appropriate row and column decoder/driver
circuitry 14 and 15.
[0022] Figure 2 illustrates a schematic circuit layout for one example of a liquid crystal
display 3 suitable for use in an electro-optic device in accordance with the invention.
[0023] In the example illustrated in Figure 2 each display element 5 is associated with
a respective switching device 16. The switching devices 16 may be of any suitable
form (for example non-linear resistive elements such as metal-insulator-metal or p-i-n
thin film diodes) but are in the example shown provided as thin film transistors (TFTs).
[0024] Each TFT 16 has its gate electrode coupled to the associated row conductor 12. One
of the main (source and drain) electrodes of each TFT 16 is coupled to the associated
column conductor 13 and the other to one electrode 5a of the associated display element
5. Although not shown in Figures 1 or 2, twisted nematic liquid crystal material is
sandwiched in known manner between the substrate 2 and a transparent, generally ITO,
common electrode 5b of the display element 5 carried by a further transparent substrate.
For the sake of simplicity and in accordance with normal practice the display elements
5 are shown in Figure 2 as capacitors. The first substrate 2 and the further transparent
substrate (not shown) are generally provided in known manner externally with polariser
layers and internally with alignment layers.
[0025] In operation of the display 3, light entering the first substrate 2, generally light
from a simple uniform light source L, is modulated according to the light transmission
characteristics of the display or picture elements 5 with, of course, the light transmission
characteristics of each picture element 5 being controlled by the voltage signals
applied to the associated row and column conductors 12 and 13 by the row and column
decoder and drive circuitry 14 and 15. The circuitry 14 and 15 may be of any suitable
conventional form, for example as described in EP-A-488455 (to which reference may
be made for further details) and will not be discussed in detail here. Generally,
the display 3 will be driven on a row at a time basis by scanning the row conductors
12 sequentially with a gating signal so as to turn on each row of TFTs 16 in turn
and applying data (video) signals corresponding, for example, to a TV line or similar
to the column conductors 13 for each row of picture elements 5 in turn as appropriate
and in synchronism with the gating signal so as to build up a complete display picture
or image.
[0026] As illustrated in Figure 1, the second array 7 carried by the second substrate 6
is provided opposite, as shown over, the display 3 so that the photosensitive elements
11 on the second substrate 6 can receive light from selected ones of the display elements
5. In this example, the photosensitive elements 11 are provided around the periphery
7a (shown in dashed lines) of the second array 7 and are associated with corresponding
peripheral picture elements 5' of the display 3 with, in this example, each photosensitive
element 11 being associated with one particular peripheral display element 5'. Of
course, other arrangements for the location of the photosensitive elements 11 and
the corresponding picture elements 5' may be possible. Providing the photosensitive
elements 11 and corresponding picture elements 5' around the peripheries of their
respective arrays 4 and 7 has however advantages in that there should be no interference
with the normal operation of the display 3 and the second array 7. In addition such
an arrangement should make it relatively simple to shield the photosensitive elements
11 from extraneous light.
[0027] In the example illustrated in Figure 1, the second array 7 is shown simply as a two
dimensional matrix array 7 of rows n
e and columns m
e of rectangular blocks representing the elements 8 with each row n
e of elements 8 being associated with a respective row conductor 9 and each column
m
e being associated with a respective column conductor 10 so that, as in the case of
the display 3, each element 8 is accessible by a unique pair of row and column conductors
9 and 10.
[0028] The elements 8 may be any type of element which can be electro-optically controlled.
For example, the elements 8 could be memory elements such as thin film transistors
which store charge representing logical '1's and '0's according to the voltages applied
to the row and column conductors 9 and 10 so that the second array 7 forms a E
2PROM (electrically erasable programmable ROM) type memory of a type, for example,
similar to that described in our pending UK Patent Application No. 9217743.5 filed
on 19th August, 1992. Any suitable form of data could be stored in such a memory array
and the second substrate 6, with a suitable battery power source if necessary, may
be readily transported to other locations and could for example form a so-called smart
card which may carry security data to enable access to buildings etc. and/or data
such as image or audio data which can be displayed or output as video or audio signals
by suitable equipment upon insertion of the card.
[0029] In another example, the elements 8 could be elements whose optical properties may
be altered either solely electrically by voltage signals input to the row and column
conductors 9 and 10 or by a combination of the voltage signals input to the row and
column conductors 9 and 10 and light incident on the elements 8. Such an array 7 could
be optically readable and could again carry security, video and/or audio data.
[0030] Where it is desirable for the second array 7 to be transported in a 'programmed'
state as discussed above, then some means, for example mechanical shutters of the
type commonly used on computer discs and the like, should be provided on the second
array 7 in a manner such that the photosensitive elements 11 are only exposed to light
when the second array 7 is in position over the first array or display 3.
[0031] In another example the second array 7 may comprise an image sensor consisting of
a two-dimensional array of photosensitive elements again accessed by the row and column
conductors 9 and 10. Any suitable form of photosensitive elements may be used, for
example photosensitive thin film transistors, or photosensitive non-linear resistive
elements such as Schottky diodes, thin film diodes, or photosensitive p-i-n diodes.
[0032] Figure 3 illustrates one possible circuit layout for the second array 7 where the
elements 8 comprise photosensitive p-i-n diodes.
[0033] In the example illustrated in Figure 3, each element 8 is coupled between a unique
pair of row and column conductors 9 and 10 and comprises a photosensitive p-i-n diode
8a in series with a switching diode 8b so that the anodes of the two diodes 8a and
8b are coupled together. The switching diodes 8b will generally be of similar construction,
although possibly of smaller area, to the photosensitive diodes 8a but will of course
be shielded from any incident light. Of course, other arrangements are possible. Thus,
for example the switching elements may be three terminal devices such as thin film
transistors (TFTs) as described in, for example, US-A-4382187 or each photosensitive
diode 8a may form both the photosensitive element and the switching element and may
simply be provided in series with a charge storage capacitor as shown in, for example,
EP-A-233104 and US-A-4945242.
[0034] In the example illustrated in Figure 3, each row conductor 9 is coupled via a respective
photosensitive diode 11a to a voltage supply line 17 connected to a positive potential
V
sel and via a respective switching diode 18 to a voltage supply line 19 connected to
a potential V
rst. This forms the row drive circuitry 90. Each column conductor 10 is coupled via a
respective photosensitive diode 11b, a capacitor C and a connection line 20 to a charge
sensitive amplifier 21 of any known suitable form and via the photosensitive diode
11b and a respective further photosensitive diode 11c to a reference potential V
cref supply line 22 to provide the column read-out circuitry 100. The photosensitive diodes
11 are of course oriented so as to be in a blocking condition until illuminated as
will be explained below.
[0035] Such an image sensor array 7 may be permanently or movably mounted to the display
3 and may be used, for example, to enable data to be input to the display using a
light pen or the like so enabling a user to enter information or alter the image shown
on the display 3 by 'writing' on the surface of the electro-optic device 1. Although
where the elements 8 of the second array 7 comprise photosensitive diodes it would
be very difficult to make the second array 7 transportable separately of the first
array while retaining the image stored at the second array and shielding the second
array 7 from ambient light, forming the device so that the image sensor array 7 is
removably mounted to the display 3 enables the image sensor array 7 to be removed
when not in use to allow for better viewing of the display 3 and also allows the same
image sensor array 7 to be used with several different displays 3.
[0036] The voltages V
sel, V
rst and V
cref may be supplied by an appropriate voltage source which could be an appropriate battery
together with suitable voltage reference providing means located on or attached to
the second substrate 6. Where, the second substrate 6 is permanently fixed to the
display 3, then the voltage supply necessary for the second array 7 could be provided
from the power supply used for the display 3.
[0037] Depending upon the particular application of the electro-optic display 1, it may
be desirable for the second array 7 to be as transparent as possible so that viewing
of the display 3 is not unduly obscured by the second array 7. This is especially
the case where the second array 7 comprises an image sensor array which may be used
to 'write' upon the display 3. The amount of area of the image array 7 which is transparent
may be optimised by using transparent materials where possible, for example by using
indium tin oxide to form the plates of any capacitors, and by careful positioning
of those components such as the photosensitive and switching diodes 8a and 8b in the
example given above which by virtue of their operation or construction cannot be transparent.
Generally, to provide the required degree of electrical conductivity, it is necessary
to form the row and column conductors 9 and 10 of opaque conductive material for example
chromium or chromium followed by aluminium. In such a case, at least the photosensitive
diodes 8a and 8b may be formed on top of the row conductors 9.
[0038] The photosensitive elements 11 may have a construction similar to that of the photosensitive
diodes 8a. The photosensitive elements 11 need of course to be shielded from light
directly incident on the second array 7. Where the photosensitive elements 11 are
provided around the periphery of the array 7 then this may be achieved quite simply
by a suitable opaque frame surrounding the array 7. Such a frame may simply be provided
by the final housing of the electro-optic device 1 without the need for any additional
components.
[0039] The photosensitive elements 11 may receive light directly from the selected ones
5' of the display 3 in which case the lower electrode of the photosensitive elements
11 should of course be formed of a transparent material such as indium tin oxide or
at least provided with an aperture for the passage of light. As a possible alternative,
the photosensitive elements 11 may receive light indirectly from the selected display
elements 5' by providing a reflective layer over the photosensitive elements 11 to
reflect light passing through the substrate 2 from the selected display elements 5'
back down onto the photosensitive elements 11. Such a reflector could of course also
serve to shield the photosensitive elements 11 from light which is directly incident
on the second array 7.
[0040] The photosensitive and switching diodes 8a and 8b could of course simply be formed
one on top of another on the row conductors 9 with of course the photosensitive diodes
8a at the top in a manner similar to that described in US Patent No. 5003167.
[0041] Figures 4 to 8 illustrate by way of a schematic plan view and cross-sectional views
one possible example of a layout for the image sensor array 7 shown in Figure 3.
[0042] As illustrated, the second array is formed using thin film technology on the substrate
6. The substrate 6 is in this case transparent and is formed of any suitable glass
or plastics material. Indeed where the image sensor array 7 is permanently provided
on the display 3 then the substrate 6 could also provide the top glass plate of a
conventional LCD display.
[0043] A first electrically conductive layer, generally a chromium layer, is deposited onto
the substrate 6 and patterned to define the row conductors 9, the cathode electrodes
23 of the switching diodes 8b, the voltage supply line 17 (which also forms the cathode
electrodes of the photosensitive elements 11a) and the cathode electrodes 24 of the
switching diodes 18. The first metal layer also provides the cathode electrodes 25
and 26 of the photosensitive elements 11b and 11a and the line 20 which also forms
the lower plates of the capacitors C.
[0044] The various diodes 8a,8b,11a,11b,11c and 18 are then formed by depositing and patterning
appropriately doped semiconductor layers. In this example, the diodes are all amorphous
silicon n-i-p diodes formed by in sequence n conductivity, intrinsic and p conductivity
type amorphous silicon layers.
[0045] An insulating layer, generally silicon nitride or some other suitable, in this case,
transparent insulator, is then deposited and defined to leave regions 27 forming the
dielectric regions of the capacitors C and necessary insulation regions 28 defining
contact windows to enable a second subsequent metal layer, again generally a chromium
(possibly covered by an aluminium) layer to be deposited and patterned to define the
column conductors 10 contacting, as shown in Figures 5 and 8, the electrodes 23 and
26, first connection electrodes 29 each connecting the anodes of the associated photosensitive
and switching diodes 8a and 8b with, of course, the first connection electrodes 29
arranged as shown in Figure 5 to shield the switching diodes 8b from any light incident
on the second array 7 but to allow light to pass to the photosensitive diodes 8a.
[0046] As is known in the art, the photosensitive diodes 8a (and for ease of manufacture
the switching diodes 8b) may have a transparent top layer of indium tin oxide which
protects the diode structure during patterning of the insulator and second metal layers.
[0047] The second metal layer defines second connection electrodes 30 providing electrical
connection between the row conductors 9 and the associated anodes of the photosensitive
diodes 11a and third connection electrodes 31 each connecting the associated row conductor
9 to the associated switching diode 18. The third connection electrodes 31 also act
to shield the switching diodes 18 from incident light. The second metal layer also
provides the voltage supply line 19 and its connections to the cathode electrodes
24 of the switching diodes 18 and the connection line 22. Fourth connection electrodes
32 each forming the other plate of the associated capacitor and connecting together
the anodes of the associated photosensitive diodes 11b and 11c may also be formed
of the second metal layer but could if desired, and at the expense of an increased
resistance, be formed of a transparent conductive material such as indium tin oxide.
[0048] As can be seen rom Figures 4, 6 and 8, the layout of the electro-optic device 1 is
organised so that there are transparent areas arranged mainly by the insulating regions
27,28 and any transparent electrodes which enable light from the selected ones 5'
of the display elements to pass through the second array 7 and be reflected by a reflective
layer. This reflective layer may form part of the housing (not shown) of the second
array 7 or the combined electro-optic device 1 or could be, as shown, a reflective
layer provided as discrete regions 33 on top of a transparent, for example polyimide,
passivating layer 34 provided over the peripheral region 7a of the second array 7.
The free surface of the passivating layer 34 may be covered in the region of the periphery
7a of the second array 7 between the reflective regions 33 by a light absorbing layer
35 so as to avoid undesired reflections onto the photosensitive elements 11a,11b,11c.
As shown in Figures 5,6 and 8, the passivating layer 34 (or a subsequent layer) may
be shaped to define a microlens array in a manner described in, for example, EP-A-154962
with the lens elements in the peripheral region only being covered by deposited reflective
material so that the microlens elements 36 over the main part of the second array
7 each serve to concentrate incident light onto the photosensitive elements 8a while
the reflectively coated microlens elements 37 serve to reflect and concentrate light
from the display transmitted through the substrate 6 onto the photosensitive elements
11a,11b,11c.
[0049] As one possible alternative to the use of the reflective regions 33, the electrodes
17, 25 and 26 could as mentioned above be formed either with apertures or of a transparent
material such as indium tin oxide so enabling light from the selected ones 5' of the
display elements 5 to be directly incident on the photosensitive elements 11a,11b,11c.
As will be appreciated by those skilled in the art where the photosensitive elements
11a,11b,11c are illuminated from beneath, it may be desirable to alter the order of
growth of the semiconductor layer so that p-i-n rather than n-i-p diodes are formed.
This would of course also require some alteration of the first and second metal layer
patterns to define the appropriate interconnections.
[0050] Figure 9 illustrates, by way of a cross-sectional view similar to Figure 8, a modified
form of the second array in which, as mentioned above, the photosensitive elements
11a,11b,11c are provided with lower electrodes 25,26 formed with apertures A so that
the photosensitive elements 11a, 11b, 11c are sensitive to light incident on the substrate
6 and passing through the apertures A. As shown in Figure 6, the substrate 6 (or a
layer provided on the substrate 6) may be formed with a microlens array so that a
respective lens element 37 is arranged to concentrate light onto an associated photosensitive
element 11a,11b or 11c via the respective aperture A. In this case the passivating
layer 34 is covered by a light absorbing layer 35 in the region of the peripheral
photosensitive elements 11a, 11b, 11c.
[0051] There may also be circumstances, if it is desired to manipulate or combine images,
where it is desirable for the photosensitive elements 8a of the second array to react
to light incident on them from the display 5 instead of or in addition to reacting
to light incident on them from above in which case the appropriate regions of the
row conductors 9 may be formed with apertures or of a transparent material or a reflective
system such as described above for the peripheral photosensitive diodes 11a,11b and
11c could be used.
[0052] It will of course be appreciated that, although Figure 3 shows the photosensitive
and switching diodes 8a and 8b as having their anodes coupled the diodes could be
reversed so as to have their cathodes connected. In addition, the switching diode
8b rather then the photosensitive diode 8a could be connected directly to the associated
row conductor 9. It will of course be understood by those skilled in the art that
either of these modifications may of course require appropriate changes in the polarities
of the voltages applied to the second array 7.
[0053] The operation of an electro-optic device 11 having as the second array 7 an image
sensor with the circuit layout shown in Figure 3 will now be described with the help
of Figure 10.
[0054] As in a conventional image sensor, the second array 7 is read out by selecting each
row in turn.
[0055] In the example illustrated in Figure 3, each row conductor 9 is, as described above,
connected to a photosensitive diode 11a and a switching diode 18 with the photosensitive
diodes 11a being connected to the voltage supply line 17 and the switching diodes
18 being connected to the voltage supply line 19.
[0056] Immediately before a given row is read out the selected picture elements 5' are controlled
by the display row and column drive circuitry 14 and 15 so as not to illuminate the
photosensitive diodes 11a. The voltage V
rst on the voltage supply line 19 is then pulsed negative as indicated by the line a
in Figure 10 so turning on all the switching diodes 18 so that the voltage of each
row conductor 5 falls as indicated by the solid line in Figure 10 to V
unsel. When the voltage V
rst on the line 19 again goes high after the pulse the row conductors 5 are held (as
indicated by the dashed line b in Figure 10) at the V
unsel voltage by virtue of the row capacitance shown schematically in Figure 3 by the capacitors
C
r shown in dashed lines. The row capacitance could be simply that of the diodes and
cross-overs on the row or may be an additional component provided at the periphery
7a of the second array 7.
[0057] The required row ne is then selected by using the row and column drive circuitry
14 and 15 of the display 5 to cause the appropriate ones of the peripheral display
elements 5' to transmit light to illuminate the peripheral photosensitive diode 11a
associated with the required row. The photo current generated within the illuminated
peripheral photosensitive diode 11a charges the row capacitance C
r and raises the row voltage (as indicated by line in Figure 10) close to V
se1 which selects the row. The voltage V
se1 turns on the switching diodes 8b in each of the elements 8a in the selected row and
a current flows through the element or pixel 8, charging the intrinsic capacitance
of the photosensitive diode 8b to a known value. The amount of charge required is
equal to the amount of charge generated by light incident on the photosensitive diode
8a.
[0058] This charge is detected by the column read-out circuitry 100 in the following manner.
[0059] Thus, when the required row is selected as discussed above, the appropriate ones
of the peripheral display elements 5' of the display 5 are controlled so as to transient
light to illuminate the photosensitive diodes 11b as well as the photosensitive diode
11a of the selected row. The photosensitive diodes 11c are not illuminated at this
time. The current flowing through each element 8 of the selected row flows down the
associated column conductor 10 to the column capacitor C until the element or pixel
8 has been recharged to its starting point as indicated by the point x in Figure 10.
The row is then de-selected by the application of the next voltage reset pulse V
rst via the switching diodes 18 and the appropriate ones of the peripheral display elements
5' are controlled so that the photosensitive diodes 11a and diodes 11b are no longer
illuminated.
[0060] At this stage, the column capacitors C will have been charged by the associated photosensitive
diodes 11b.
[0061] The appropriate ones of the peripheral display elements 5' of the display are then
controlled so as to illuminate the photosensitive elements 11c one by one in sequence.
When the photosensitive diode 11c associated with a particular column conductor C
is connected to a reference potential V
ref and a current then flows from the charge-sensitive amplifier 21 to discharge the
column capacitor C. This places the packet of charge from the element or pixel photosensitive
diode 8a onto the feedback capacitor (not shown) of the charge-sensitive amplifier
21. The amplifier output voltage can then be sampled and subsequently processed using
conventional means.
[0062] Each row of the second array 7 is sequentially addressed in the same manner. When
a row is not being read out the switching diodes 8b are not rendered conducting and
so photogenerated charge is stored on the intrinsic capacitance of the photosensitive
diodes 8a of the row. The period when this is happening is known as the integration
period because effectively the charge stored at a photosensitive element 8a during
this period represents an integral over the time the row is unselected of light incident
on the photosensitive element 8a.
[0063] In a video type of sensor, the process of reading the rows will be carried out continously,
that is the first row is read again after the last row and so on so that for N rows
and a read-out time per row of t
R the integration period is t
2 = N.t
R.
[0064] Where the image sensor is being used, for example, to scan a document then generally
only a single read of the second array 2 will be required so that in that case the
integration time would be the time since the light source illuminating the document
was turned on. Where the image sensor array 7 is sufficiently transparent then the
main display elements 5 of the display 3 may be used to illuminate a document placed
over the image sensor array 7 so enabling the document to be in intimate contact with
the second array 7.
[0065] Figure 11 illustrates a modified version of the circuit layout shown in Figure 3.
As will be evident from a comparison of Figures 3 and 11, the two differ in the construction
of the row read-out circuitry 90' and the column read-out circuitry 100'.
[0066] As shown in Figure 11, the switching diodes 18' are reversed in comparison to the
switching diodes 18 shown in Figure 3 (that is the diodes 18' have their anodes connected
to the supply line 19). The diodes 18' are also photosensitive, that is they have
a similar structure to the diodes 11a. In this arrangement, the reset pulse V
rst can be applied to the row conductors 9 by illuminating the photosensitive diodes
18' appropriately. This arrangement has the advantage that the supply lines 17 and
18 need only supply constant (that is not pulsed) voltages and so these voltages may
be provided by a suitable battery which can be mounted to the substrate 6.
[0067] As a further alternative, it may be possible to replace each pair of switching and
photosensitive diode 18 and 11a by a single photosensitive diode (because the forward
current of a diode is much higher than the photocurrent) and to enable resetting by
applying a different voltage to the single voltage supply line.
[0068] In a second array 7' having the modified circuit layout shown in Figure 11, each
column conductor 10 is associated with two photosensitive diodes 11b and 11'b, two
photosensitive diodes 11c and 11'c and two column capacitors C and C'. All of the
photosensitive diodes 11c and 11'c have their anodes coupled to the voltage reference
line 22. The capacitors C are coupled via the connection line 20 to a charge sensitive
amplifier 21 and the capacitors C1 coupled via a connection line 20' to a charge sensitive
amplifier 21'.
[0069] In operation of an image sensor array 7 having the circuit layout shown in Figure
11, while the appropriate ones of the peripheral display elements 5' are illuminating
the photosensitive elements 11a associated with the n+1 th row and the photosensitive
elements 11'b to enable the charge accumulated by the elements 8 of the n+1 th row
to be transferred to the column capacitors C', the photosensitive elements 11c are
illuminated one by one in sequence by the appropriate ones of the peripheral display
elements 5' so as to discharge the column capacitors C as discussed above with reference
to Figure 3 to transfer the charge to the feedback capacitor of the charge sensitive
amplifier. Thus, while the first stage of the row read-out operation is being carried
out in respect of one row (the n+1 th in this example), the second stage can be carried
out in respect of the preceding row (the nth row) so reducing the overall time required
to read-out all rows of the second array 7 by about one half.
[0070] Although in the examples described above, all of the column conductors 10 of the
second array 7 are coupled to a single charge sensitive amplifier 21 in the case of
Figure 3 and two in the case of the Figure 11 arrangement, the number of charge sensitive
amplifiers 21 could be increased so that a given number
(where m is the number of columns and y the number of charge sensitive amplifiers
21 in the Figure 3 arrangement or the number of pairs of charge sensitive amplifiers
21 and 21' in the Figure 10 arrangement) up to a maximum where y=m, so enabling y
columns to be read-out simultaneously and thus reducing the total read-out time for
the second array 7 by a factor y.
[0071] Although the photosensitive diodes 11a,11b and 11c and switching diodes 18 have been
shown in the Figures as being of similar structure to the photosensitive and switching
diodes 8a and 8b, they may be of different geometry, for example of larger area, so
as to provide the current handling capability required and they could if considered
desirable be p-i-n as opposed to n-i-p diodes, for example. Of course, the modified
row read-out circuitry 90' or the modified column read-out circuitry 100' shown in
Figure 11 could be used in the example shown in Figure 3.
[0072] It is of course important that the photosensitive elements 11a, 11b, 11c are sufficiently
well spaced from adjacent similar photosensitive elements 11a, 11b, 11c that there
is no significant cross-talk between the photosensitive elements 11a, 11b, 11c. Depending
upon the relative pitches of the display array 4 and the second array 7 and the separation
of the second array 7 from the first or display array 4, there may be no problems
presented by providing the photosensitive elements 11a,11b,11c at a pitch similar
to the row and column conductors 9 and 10. However, in order to reduce the possibilities
of any such cross-talk the photosensitive elements 11a,11b and 11c may be staggered
as shown in the schematic plan view in Figure 12 in a direction along the length of
the associated row or column conductors 9 or 10 so as effectively to increase the
spacing between adjacent photosensitive elements 11a, 11b, 11c.
[0073] In the example illustrated in Figure 12, the photosensitive elements 11a are staggered
so that in a direction along the row conductors 9, the n, n+3, etc. photosensitive
elements 11a are aligned, that is so that each fourth element 11a is aligned. The
spacing of the adjacent photosensitive elements 11a will of course depend upon the
design rules of the device and any constraints on the overall size of the device.
Any suitable staggered pattern may however be adopted.
[0074] The photosensitive diodes 11b and 11c may be similarly staggered with, of course,
the photosensitive diodes 11b and 11c associated with a respective column conductor
being themselves spaced apart along the direction of the column conductor 10.
[0075] Generally all of the photosensitive elements 11a,11b,11c will be spaced by a similar
distance from the associated display element 5' and so may have a similar spacing
from one another. Normally the lateral spacing of the display elements 5' should be
greater than the vertical separation between each display element 5' and the associated
photosensitive element 11a,11b,11c.
[0076] In the examples described above, each row and each column conductor 9 and 10 is coupled
via a single photosensitive element 11a, 11b, 11c to the associated voltage supply
or connection line 17,20 and 22. However this need not necessarily be the case and,
for example, an arrangement similar to that described in EP-A-488455 could be used
in which, for example, each row conductor 9 is associated with one or more photosensitive
elements 11a each aligned with a respective different column of periperal display
elements 5' so that the row conductor 9 is only connected to the voltage supply line
17 when all of the associated photosensitive diodes 11a are rendered conducting. An
example of such a pattern of photosensitive elements 11a is illustrated schematically
in the diagram in Figure 13. In Figures 12 and 13 the dashed lines numbered 14a to
14e represent columns of peripheral display elements 5' of the display 5.
[0077] In such an arrangement cross-talk between photosensitive diodes 11a associated with
adjacent row conductors 9 does not present significant problems because, of course,
each row conductor 9 will only be coupled to the voltage supply line V
sel if all of the associated photosensitive elements 11a are rendered conducting.
[0078] A similar structure could be used for the photosensitive diodes 11b,11c associated
with the column conductors 10 where appropriate, for example where it is required
to switch individual photosensitive diodes.
[0079] EP-A-488455 describes the use of transistor, generally TFT buffers, to provide higher
currents for charging the row capacitance and a similar idea could be used in the
present device to increase the row select current.
[0080] Where, as discussed above, it is desirable for the second array 7 to be sufficiently
transparent to enable the display 3 to be viewed through the second array 7 then the
image sensor transparency could be increased in a manner similar to that described,
in our copending UK Patent Application No. 9209734.4 filed on 6th May 1992 which describes
structures in which the number of row and column conductors in the second array 7
can be decreased by associating a number of photosensitive elements 8a with the same
pair of row and column conductors 9 and 10 and providing some form of threshold adjustment
means so that different voltage levels are required to assess different ones of the
photosensitive elements 8a associated with the same pair of row and column conductors
9 and 10.
[0081] The second array 7 could be any suitable type of array for example an array of electro-optically
adjustable memory elements or photosensitive elements as discussed above or touch
sensitive elements. In addition the second array 7 could be another display controllable
by the display 3 to allow superposition of images. Although this may present parallax
problems it could be of advantage where an image is derived from a conventional analogue
TV or video signal. Also, although in the examples described above the display array
4 and the second array 7 are both two dimensional active matrix arrays, this need
not necessarily be the case and one or other of the arrays 4 and 7 may be one dimensional
and/or a passive array.
1. An electro-optic device comprising a first substrate (2) carrying an electro-optic
display (3) having a first array (4) of display elements (5) and conductors (12, 13)
for addressing display elements to enable the display to display an image, a second
substrate (6) carrying a second array (7) of elements (8) addressable by conductors
(9, 10) and photosensitive elements (11) associated with the conductors (9, 10) for
supplying, when illuminated, signals along the conductors for accessing the elements
(8) of the second array (7), the second substrate being provided opposite the first
substrate (2) so that the photosensitive elements (11) are associated with selected
ones (5') of the display elements (5) for enabling the selected display elements to
illuminate the photosensitive elements allowing access of the elements of the second
array to be controlled by the display.
2. An electro-optic device according to Claim 1, wherein the electro-optic display (3)
comprises a two-dimensional matrix array of display elements (5) arranged in row and
columns with associated row and column conductors (12, 13) and the second array (7)
is a two-dimensional array of elements (8) arranged in rows and columns with row and
column conductors (9, 10) being associated with the elements of the second array so
that supplying signals to a selected row conductor and a selected column conductor
of the second array accesses an element of the second array and wherein the row and
column conductors of the second array are associated with photosensitive elements
(11) for supplying, when illuminated by selected ones of the display elements, signals
along the row and column conductors for accessing the elements of the second array.
3. An electro-optic device according to Claim 2, wherein each element (8) of the second
array (7) is arranged to store charge and each row conductor (9) of the second array
is coupled to a select voltage supply line (17) via at least one respective photosensitive
element (11) so that in operation of the electro-optic device in order to read charge
stored at the element within a row the at least one photosensitive element associated
with the row is illuminated by the display to couple the select voltage to the row
conductor.
4. An electro-optic device according to Claim 3, wherein each row conductor (9) of the
second array (7) is coupled to a reset voltage supply line (19) via a respective switching
element (18) for enabling a reset voltage pulse to be applied to the row conductor
to reset the associated elements.
5. An electro-optic device according to Claim 3 or 4, wherein each column conductor (10)
of the second array (7) is connected by at least one first photosensitive element
(11) to one electrode of a respective column capacitor (C) having its other electrode
coupled to a charge sensitive amplifier (21) and to at least one second photosensitive
element (11) which is coupled to a voltage reference line (22) so that, in order to
read charge from an element within a given column of the second array, first the associated
at least one first photosensitive element is illuminated by the display for allowing
the charge stored at an element in both the column and a row to which the select voltage
is applied to be transferred via the column conductor and the at least one first photosensitive
element to the capacitor and then the at least one second photosensitive element is
illuminated to allow the charge stored at the column capacitor to be transferred to
the charge sensitive amplifier.
6. An electro-optic device according to Claim 3 or 4, wherein each column conductor (10)
is coupled to one electrode of each of first and second column capacitors (C, C')
by respective first photosensitive elements (11b, 11b') with each capacitor having
its other electrode coupled to a respective charge sensitive amplifier (21, 21') and
to a respective second photosensitive element (11c, 11c') coupled to a voltage reference
line (22) so that, in order to read charge from an element within a given column of
the second array, first one of the associated first photosensitive elements is illuminated
by the display for allowing the charge stored at an element in both the column and
a row to which the select voltage is applied to be transferred via the column conductor
and the said one first photosensitive element to the associated one of the first and
second capacitors and then the one of the second photosensitive elements is illuminated
to allow the charge stored at the column capacitor to be transferred to the charge
sensitive amplifier.
7. An electro-optic device according to any of the preceding claims, wherein the photosensitive
elements (11) are arranged at the periphery of the second array (7).
8. An electro-optic device according to any one of the preceding claims, wherein each
conductor (9, 10) of the second array is associated with at least one respective photosensitive
element (11).
9. An electro-optic device according to any one of the preceding claims, wherein each
conductor (9, 10) of the second array (7) is associated with a number of photosensitive
elements (11) arranged such that signals are only supplied along the conductor when
all of the associated photosensitive elements are illuminated.
10. An electro-optic device according to any one of the preceding claims, wherein the
photosensitive elements (11) associated with adjacent conductors are staggered so
that the spacing between the photosensitive elements associated with adjacent conductors
is greater than the spacing between the adjacent conductors.
11. An electro-optic device according to any one of the preceding claims, wherein the
first and second arrays (4, 7) are of comparable size and the display elements (5)
for illuminating the photosensitive elements are provided at the periphery of the
first array.
12. An electro-optic device according to any one of the preceding claims, wherein the
display comprises a liquid crystal display.
13. An electro-optic device according to any one of the preceding claims, wherein the
second array (7) comprises an array of further photosensitive elements (8a).
14. An electro-optic device according to any one of the preceding claims, wherein the
second substrate (6) carrying the second array (7) is mounted to the first substrate
(2) carrying the first array (4).
15. An electro-optic device according to any one of the preceding claims, wherein the
second substrate (6) carrying the second array is separable from the first substrate
carrying the first array.
1. Elektrooptische Anordnung mit einem ersten Substrat (2) mit einer elektrooptischen
Wiedergabeanordnung (3) mit einer ersten Anordnung (4) von Wiedergabeelementen (5)
und Leitern (12, 13) zum Adressieren von Wiedergabeelementen um die Wiedergabeanordnung
in den Stand zu bringen, ein Bild wiederzugeben, mit einem zweiten Substrat (6) mit
einer zweiten Anordnung (7) von Elementen (8), die durch Leiter (9, 10) und photoempfindliche
Elemente (11), die den Leitern (9, 10) zugeordnet sind, adressierbar sind, um, wenn
sie beleuchtet werden, Signale zu liefern, und zwar über die Leiter zum Zugreifen
auf die Elemente (8) der zweiten Anordnung (7), wobei das zweite Substrat gegenüber
dem ersten Substrat (2) derart vorgesehen ist, dass die photoempfindlichen Elemente
(11) selektierten Wiedergabeelementen (5') der Wiedergabeelemente (5) zugeordnet sind,
damit es ermöglicht wird, dass die selektierten Wiedergabeelemente die photoempfindlichen
Elemente beleuchten, wodurch Zugriff auf die Elemente der durch die Wiedergabeanordnung
zu steuernden zweiten Anordnung ermöglicht wird.
2. Elektrooptische Anordnung nach Anspruch 1, wobei die elektrooptische Wiedergabeanordnung
(3) eine zweidimensionale Matrixanordnung von Wiedergabeelementen (5) aufweist, die
in Reihen und Spalten mit zugeordneten Reihen- und Spaltenleitern (12, 13) vorgesehen
sind und die zweite Anordnung (7) eine zweidimensionale Anordnung von Elementen (8)
sein kann, die in Reihen und Spalten mit Reihen- und Spaltenleitern (9, 10) angeordnet
sind, wobei diese Leiter den Elementen der zweiten-Anordnung zugeordnet sind, so dass
das Zuführen von Signalen zu einem selektierten Reihenleiter und einem selektierten
Spaltenleiter der zweiten Anordnung auf ein Element der zweiten Anordnung zugreift
und die Reihen- und Spaltenleiter der zweiten Anordnung photoempfindlichen Elementen
(11) zugeordnet sind um, wenn durch selektierte Wiedergabeelemente beleuchtet, über
die Reihen- und Spaltenleiter Signale zu liefern zum Zugreifen auf die Elemente der
zweiten Anordnung.
3. Elektrooptische Anordnung nach Anspruch 2, wobei jedes Element (8) der zweiten Anordnung
(7) dazu vorgesehen ist, Ladung zu speichern und jeder Reihenleiter (9) der zweiten
Anordnung über wenigstens ein betreffendes photoempfindliches Element (11) mit einer
Selektionsspannungsspeiseleitung (17) gekoppelt ist, so dass im Betrieb der elektrooptischen
Anordnung zum Auslesen in dem Element innerhalb einer Reihe gespeicherter Ladung das
wenigstens eine photoempfindliche Element, das der Reihe zugeordnet ist, durch die
Wiedergabeanordnung beleuchtet wird zum Koppeln der Selektionsspannung mit dem Reihenleiter.
4. Elektrooptische Anordnung nach Anspruch 3, wobei jeder Reihenleiter (9) der zweiten
Anordnung (7) über ein betreffendes Schaltelement (18) mit einer Rückstellspeisespannungsleitung
(19) gekoppelt ist, damit es ermöglicht wird, dass dem Reihenleiter zum Rückstellen
der zugeordneten Elemente ein Rückstellspannungsimpuls zugeführt wird.
5. Elektrooptische Anordnung nach Anspruch 3 oder 4, wobei jeder Spaltenleiter (10) der
zweiten Anordnung (7) durch wenigstens ein erstes photoempfindliches Element (11)
mit einer Elektrode eines betreffenden Spaltenkondensators (C) gekoppelt ist, dessen
andere Elektrode mit einem ladungsempfindlichen Verstärker (21) und mit wenigstens
einem zweiten photoempfindlichen Element (11) gekoppelt ist, das mit einer Spannungsbezugsleitung
(22) derart gekoppelt ist, dass zum Auslesen von Ladung aus einem Element innerhalb
einer bestimmten Spalte der zweiten Anordnung, zunächst das zugeordnete, wenigstens
eine erste photoempfindliche Element durch die Wiedergabeanordnung beleuchtet wird,
damit die Ladung, die bei einem Element in der Spalte sowie in einer Reihe gespeichert
ist, der die Selektionsspannung zugeführt wird, die über den Spaltenleiter und das
wenigstens eine erste photoempfindliche Element zu dem Kondensator übertragen werden
soll, ausgelesen wird, und dass danach das wenigstens eine zweite photoempfindliche
Element beleuchtet wird, damit die Ladung, die in dem Spaltenkondensator gespeichert
ist, zu dem ladungsempfindlichen Verstärker übertragen wird.
6. Elektrooptische Anordnung nach Anspruch 3 oder 4, wobei jeder Spaltenleiter (10) durch
betreffende erste photoempfindliche Elemente (11b, 11b') mit einer Elektrode des ersten
sowie des zweiten Spaltenkondensators (C, C') gekoppelt ist, wobei von jedem Kondensator
die andere Elektrode mit einem betreffenden ladungsempfindlichen Verstärker (21, 21')
sowie mit einem betreffenden zweiten photoempfindlichen Element (11c, 11c') gekoppelt
ist, das derart mit einer Spannungsbezugsleitung (22) gekoppelt ist, dass zum Auslesen
von Ladung aus einem Element innerhalb einer bestimmten Spalte der zweiten Anordnung,
zunächst eines der zugeordneten ersten photoempfindlichen Elemente durch die Wiedergabeanordnung
beleuchtet wird, damit die Ladung, die bei einem Element in der Spalte sowie in einer
Reihe gespeichert ist, der die Selektionsspannung zugeführt wird um über den Spaltenleiter
und das genannte erste photoempfindliche Element zu dem betreffenden ersten und zweiten
Kondensator und danach zu dem einen der zweiten photoempfindlichen Elemente übertragen
zu werden, beleuchtet wird, damit die Ladung, die im Spaltenkondensator gespeichert
ist, zu dem ladungsempfindlichen Verstärker übertragen wird.
7. Elektrooptische Anordnung nach einem der vorstehenden Ansprüche, wobei die photoempfindlichen
Elemente (11) an dem Umfang der zweiten Anordnung (7) vorgesehen sind.
8. Elektrooptische Anordnung nach einem der vorstehenden Ansprüche, wobei jeder Leiter
(9, 10) der zweiten Anordnung wenigstens einem betreffenden photoempfindlichen Element
(11) zugeordnet ist.
9. Elektrooptische Anordnung nach einem der vorstehenden Ansprüche, wobei jeder Leiter
(9, 10) der zweiten Anordnung (7) einer Anzahl photoempfindlicher Elemente (11) zugeordnet
ist, die derart vorgesehen sind, dass Signale nur dann über den Leiter zugeführt werden,
wenn alle zugeordneten photoempfindlichen Elemente beleuchtet werden.
10. Elektrooptische Anordnung nach einem der vorstehenden Ansprüche wobei die photoempfindlichen
Elemente (11), die benachbarten Leitern zugeordnet sind, versetzt sind, so dass der
Raum zwischen den photoempfindlichen Elementen, die den benachbarten Leitern zugeordnet
sind, größer ist als der Raum zwischen den benachbarten Leitern.
11. Elektrooptische Anordnung nach einem der vorstehenden Ansprüche, wobei die erste und
die zweite Anordnung (4, 7) von einer vergleichbaren Größe sind und die Wiedergabeelemente
(5) zum Beleuchten der photoempfindlichen Elemente am Umfang der ersten Anordnung
vorgesehen sind.
12. Elektrooptische Anordnung nach einem der vorstehenden Ansprüche, wobei die Wiedergabeanordnung
eine Flüssigkristall-Wiedergabeanordnung aufweist.
13. Elektrooptische Anordnung nach einem der vorstehenden Ansprüche, wobei die zweite
Anordnung (7) eine Anordnung weiterer photoempfindlicher Elemente (8a) aufweist.
14. Elektrooptische Anordnung nach einem der vorstehenden Ansprüche, wobei das zweite
Substrat (6), das die zweite Anordnung (7) trägt, auf den ersten Substrat (2) angeordnet
ist, das die erste Anordnung (4) trägt.
15. Elektrooptische Anordnung nach einem der vorstehenden Ansprüche, wobei das zweite
Substrat (6), das die zweite Anordnung trägt, von dem ersten, die erste Anordnung
tragenden Substrat entfernbar ist.
1. Dispositif électro-optique comprenant un premier substrat (2) portant un affichage
électro-optique (3) ayant un premier réseau (4) d'éléments d'affichage (5) et de conducteurs
(12, 13) pour adresser des éléments d'affichage afin de permettre à l'affichage d'afficher
une image, un deuxième substrat (6) portant un deuxième réseau (7) d'éléments (8)
adressables par des conducteurs (9, 10) et des éléments photosensibles (11) associés
aux conducteurs (9, 10) pour délivrer, lorsqu'ils sont éclairés, des signaux le long
des conducteurs afin d'accéder aux éléments (8) du deuxième réseau (7), le deuxième
substrat étant appliqué en regard du premier substrat (2) de telle sorte que les éléments
photosensibles (11) soient associés à des éléments choisis (5') des éléments d'affichage
(5) afin de permettre aux éléments d'affichage sélectionnés d'éclairer les éléments
photosensibles, permettant ainsi de commander l'accès aux éléments du deuxième réseau
par l'affichage.
2. Dispositif électro-optique selon la revendication 1, dans lequel l'affichage électro-optique
(3) comprend un réseau matriciel bidimensionnel d'éléments d'affichage (5) agencés
en rangées et en colonnes avec des conducteurs de rangées et de colonnes associés
(12, 13) et le deuxième réseau (7) est un réseau bidimensionnel d'éléments (8) agencés
en rangées et en colonnes, les conducteurs de rangées et de colonnes (9, 10) étant
associés aux éléments du deuxième réseau de telle sorte que l'acheminement de signaux
à un conducteur de rangée choisi et à un conducteur de colonne choisi du deuxième
réseau permette d'accéder à un élément du deuxième réseau et les conducteurs de rangées
et de colonnes du deuxième réseau étant associés à des éléments photosensibles (11)
pour acheminer, lorsqu'ils sont éclairés par certains, choisis, des éléments d'affichage,
des signaux le long des conducteurs de rangées et de colonnes afin d'accéder aux éléments
du deuxième réseau.
3. Dispositif électro-optique selon la revendication 2, dans lequel chaque élément (8)
du deuxième réseau (7) est agencé pour stocker une charge et chaque conducteur de
rangée (9) du deuxième réseau est couplé à une ligne d'alimentation en tension de
sélection (17) via au moins un élément photosensible respectif (11) de telle sorte
que, lors du fonctionnement du dispositif électro-optique pour lire la charge stockée
dans l'élément au sein d'une rangée, le au moins un élément photosensible associé
à la rangée soit éclairé par l'affichage pour coupler la tension de sélection au conducteur
de rangée.
4. Dispositif électro-optique selon la revendication 3, dans lequel chaque conducteur
de rangée (9) du deuxième réseau (7) est couplé à une ligne d'alimentation de tension
de remise à zéro (19) via un élément de commutation respectif (18) pour permettre
d'appliquer une impulsion de tension de remise à zéro au conducteur de rangée afin
de remettre à zéro les éléments associés.
5. Dispositif électro-optique selon la revendication 3 ou 4, dans lequel chaque conducteur
de colonne (10) du deuxième réseau (7) est connecté par au moins un premier élément
photosensible (11) à une électrode d'un condensateur de colonne respectif (C) dont
l'autre électrode est couplée à un amplificateur sensible à la charge (21) et à au
moins un deuxième élément photosensible (11) qui est couplé à une ligne de référence
de tension (22) de telle sorte que, pour lire la charge dans un élément qui se trouve
dans une colonne donnée du deuxième réseau, tout d'abord, le au moins un premier élément
photosensible associé soit éclairé par l'affichage pour permettre à la charge stockée
dans un élément dans à la fois la colonne et une rangée à laquelle la tension de sélection
est appliquée d'être transférée via le conducteur de colonne et le au moins un premier
élément photosensible au condensateur et qu'ensuite, le au moins un deuxième élément
photosensible soit éclairé pour permettre de transférer la charge stockée dans le
condensateur de colonne à l'amplificateur sensible à la charge.
6. Dispositif électro-optique selon la revendication 3 ou 4, dans lequel chaque conducteur
de colonne (10) est couplé à une électrode de chacun des premier et second condensateurs
de colonnes (C, C') par des premiers éléments photosensibles respectifs (11b, 11b'),
chaque condensateur ayant son autre électrode couplée à un amplificateur sensible
à la charge respectif (21, 21') et à un deuxième élément photosensible respectif (11c,
11c') couplé à une ligne de référence de tension (22) de telle sorte que, pour lire
la charge dans un élément à l'intérieur d'une colonne donnée du deuxième réseau, tout
d'abord l'un des premiers éléments photosensibles associés soit éclairé par l'affichage
pour permettre à la charge stockée dans un élément à la fois dans la colonne et une
rangée à laquelle la tension de sélection est appliquée, d'être transférée via le
conducteur de colonne et ledit un premier élément photosensible au condensateur associé
du premier et du second condensateurs et qu'ensuite, le premier des deuxièmes éléments
photosensibles soit éclairé pour permettre de transférer la charge stockée dans le
condensateur de colonne à l'amplificateur sensible à la charge.
7. Dispositif électro-optique selon l'une quelconque des revendications précédentes,
dans lequel les éléments photosensibles (11) sont aménagés sur la périphérie du deuxième
réseau (7).
8. Dispositif électro-optique selon l'une quelconque des revendications précédentes,
dans lequel chaque conducteur (9, 10) du deuxième réseau est associé à au moins un
élément photosensible respectif (11).
9. Dispositif électro-optique selon l'une quelconque des revendications précédentes,
dans lequel chaque conducteur (9, 10) du deuxième réseau (7) est associé à un certain
nombre d'éléments photosensibles (11) aménagés de telle sorte que les signaux ne soient
appliqués le long du conducteur que lorsque tous les éléments photosensibles associés
sont éclairés.
10. Dispositif électro-optique selon l'une quelconque des revendications précédentes,
dans lequel les éléments photosensibles (11) associés à des conducteurs adjacents
sont échelonnés de telle manière que l'espacement entre les éléments photosensibles
associés à des conducteurs adjacents soit supérieur à l'espacement entre les conducteurs
adjacents.
11. Dispositif électro-optique selon l'une quelconque des revendications précédentes,
dans lequel les premier et deuxième réseaux (4, 7) sont de taille comparable et les
éléments d'affichage (5) destinés à éclairer les éléments photosensibles sont aménagés
sur la périphérie du premier réseau.
12. Dispositif électro-optique selon l'une quelconque des revendications précédentes,
dans lequel l'affichage comprend un affichage à cristaux liquides.
13. Dispositif électro-optique selon l'une quelconque des revendications précédentes,
dans lequel le deuxième réseau (7) comprend un réseau d'autres éléments photosensibles
(8a).
14. Dispositif électro-optique selon l'une quelconque des revendications précédentes,
dans lequel le deuxième substrat (6) portant le deuxième réseau (7) est monté sur
le premier substrat (2) portant le premier réseau (4).
15. Dispositif électro-optique selon l'une quelconque des revendications précédentes,
dans lequel le deuxième substrat (6) portant le deuxième réseau est séparable du premier
substrat portant le premier réseau.